Magnetoresistive head and manufacturing method therefor

Details Magnetoresistive head and manufacturing method therefor Magnetoresistive head and manufacturing method therefor

2001-05-09

2003-03-25

Walczak, David J. (Department: 3751)

Metal working

Method of mechanical manufacture

Electrical device making

C029S407010, C029S603100, C029S603110, C029S603150

Reexamination Certificate

active

06536099

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention.
The present invention relates to a magnetoresistive head for use in magnetic recording and playback devices, such as video tape recorders or digital audio tape recorders, so as to play back information recorded on a tapelike magnetic recording medium.
2. Description of the Related Art
Magnetic recording and playback devices, such as video tape-recorders or digital audio tape recorders, which use a magnetic tape as a recording medium, have been required to achieve a higher density and a larger capacity. Magnetoresistive heads have become applicable as playback magnetic heads which have a high sensitivity to detect signal magnetic fields and which are able to obtain a large playback output at high recording density.
FIGS. 10
to
13
show such a type of conventional magnetic recording head. In a magnetoresistive head
21
, an arc-shaped medium-sliding surface
23
, on which a magnetic tape slides, is formed at narrow end portions
22
a
of a pair of joined substrates
22
made of a nonmagnetic material. The leading ends of a magnetoresistive sensor layer
24
and marking layers
29
and
30
interposed between the substrates
22
are exposed at the medium-sliding surface
23
.
When manufacturing the magnetoresistive head
21
, as shown in
FIG. 11
, a lower gap layer (not shown) is formed on one of the substrates
22
with a lower shielding layer (not shown) therebetween, the magnetoresistive sensor layer
24
and a pair of bias layers
25
are formed on the lower gap layer, electrode layers
26
are respectively formed on the bias layers
25
, and an upper shielding layer
27
is formed thereon, thereby forming a laminated member composed of the above layers. Then, three pairs of marking layers
28
,
29
, and
30
are formed on the upper shielding layer
27
so that they are symmetrical with respect to the magnetoresistive sensor layer
24
and so that they are offset with respect to one another.
Next, the substrates
22
are joined together so as to cover the laminated member, and are subjected to cutting so as to reduce the widths of the end portions
22
a
. As shown in
FIG. 12
in a state in which the center of a belt-shaped lapping sheet
31
extending in the direction of arrow B (into the plane of the paper) is aligned with the center of the end portions
22
a
of the substrates
22
in the widthwise direction (the direction of arrow A) of the magnetoresistive sensor layer
24
, the end portions
22
a
of the substrates
22
are lapped together with the laminated member while moving the lapping sheet
31
in the direction B. As a result, as shown in
FIG. 13
the arc-shaped medium-sliding surface
23
is formed, and the leading end of the magnetoresistive sensor layer
24
is exposed at the top of the medium-sliding surface
23
.
In this case, by performing lapping while observing the marking layers
28
,
29
, and
30
exposed at the end portions
22
a
of the substrates
22
, a length H from the leading end to the rear end of the magnetoresistive sensor layer
24
can be adjusted to a predetermined value.
The conventional magnetoresistive head
21
thus configured and manufactured is assembled in a magnetic recording and playback device (not shown). The magnetoresistive head
21
is used in a state in which sensing current (steady-state current) is applied from the electrode layers
26
to the magnetoresistive sensor layer
24
, and plays back information recorded on the magnetic tape, which slides on the medium-sliding surface
23
, based on changes in resistance of the magnetoresistive sensor layer
24
.
In the above-described conventional magnetoresistive head
21
, however, by aligning the center of the lapping sheet
31
with the center of the end portions
22
a
of the substrates
22
, the medium sliding surface
23
is arc-shaped so that the magnetic tape can smoothly slide thereon, and the leading end of the magnetoresistive sensor layer
24
is exposed at the top of the arc-shaped medium-sliding surface
23
. When the end portions
22
a
of the substrates
22
vary in size in the widthwise direction (the direction A) of the magnetoresistive sensor layer
24
due to variations in working accuracy, as shown in
FIG. 14
, the leading end of the magnetoresistive sensor layer
24
is exposed at an offset position from the predetermined top of the arc-shaped medium-sliding surface
23
. As a result, a spacing is likely to be formed between the magnetic tape sliding on the medium-sliding surface
23
and the leading end of the magnetoresistive sensor layer
24
, and this may make it impossible to play back information recorded on the magnetic tape.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-described problems in the conventional art, and an object of the invention is to provide a magnetoresistive head in which a magnetoresistive sensor layer can be reliably exposed at a predetermined position of a medium-sliding surface so as to reliably play back information recorded on a magnetic tape and to provide a manufacturing method therefor.
In order to achieve the above object, according to an aspect of the present invention, there is provided a magnetoresistive head including a lower shielding layer, a magnetoresistive sensor layer formed on the lower shielding layer with a lower gap layer therebetween, and an upper shielding layer formed on the magnetoresistive sensor layer with an upper gap layer therebetween, wherein a marking layer is formed on at least one of the upper side of the upper shielding layer and the lower side of the lower shielding layer so as to be opposed to the magnetoresistive sensor layer, the leading ends of the magnetoresistive sensor layer and the marking layer are exposed at a medium-sliding surface on which a recording medium slides, a length of the leading end of the marking layer in the widthwise direction intersecting the direction of sliding of the recording medium is equal to a length from the leading end to the rear end of the magnetoresistive sensor layer, and the center in the widthwise direction of the marking layer is placed on a straight line that intersects the magnetoresistive sensor layer via the center thereof in the widthwise direction.
Since the medium-sliding surface can be formed in a state in which the center in the widthwise direction of a lapping sheet is aligned with the center in the widthwise direction of the magnetoresistive sensor layer, the leading end of the magnetoresistive sensor layer can be reliably exposed at a predetermined position on the medium-sliding surface, and information recorded on the recording medium can be played back reliably.
According to another aspect of the present invention, there is provided a magnetoresistive head including a lower shielding layer, a magnetoresistive sensor layer formed on the lower shielding layer with a lower gap layer therebetween, and an upper shielding layer formed on the magnetoresistive sensor layer with an upper gap layer therebetween, wherein a marking layer is formed on at least one of the upper side of the upper shielding layer and the lower side of the lower shielding layer so as to be opposed to the magnetoresistive sensor layer, the leading ends of the magnetoresistive sensor layer and the marking layer are exposed at a medium-sliding surface on which a recording medium slides, the marking layer is shaped so that a length thereof in the widthwise direction intersecting the direction of sliding of the recording medium changes at a fixed rate from the leading end toward the rear end, and a marker portion formed in the marking layer for detecting the center in the widthwise direction of the magnetoresistive sensor layer is placed on a straight line that intersects the magnetoresistive sensor layer via the center thereof in the widthwise direction.
Since the medium-sliding surface can be formed in a state in which the center in the widthwise direction of a lapping sheet is aligned with the center in the widthwise direction of the magnetoresistive sensor layer, the leading

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